Catheter ablation is an arrhythmia treatment method of inserting an ablation catheter into a cardiac chamber and applying heat between an electrode at a tip portion of the catheter and a counter electrode plate to ablate a myocardial tissue. The catheter ablation is conducted mainly for treatment of tachyarrhythmias such as a paroxysmal supraventricular tachycardia, an atrial tachycardia, an atrial flutter, and a paroxysmal ventricular tachycardia and is a technique of diagnosing a pathogenetic mechanism and a trigger region of an arrhythmia in a cardiac electrophysiological study, thereafter making an electrode of an ablation catheter reach the trigger region of the arrhythmia from the interior of a cardiac chamber, and repeating an operation of applying the electrode to a causative myocardial tissue in the region and heating the tissue at 50 to 65° C. for approximately 60 seconds.
Many of the ablation catheters currently in use have a metallic electrode at a tip portion of the catheter, and each of such catheters generally adopts a technique of bringing the metallic electrode into contact with a myocardial tissue in a dotted manner and forming an ablation line while moving the electrode little by little to isolate the trigger region of the arrhythmia (Patent Literature 1).
However, the ablation catheter having the metallic electrode requires several dozen times of repeated ablations to form the ablation line and isolate the trigger region of the arrhythmia and thus causes problems of a prolonged operation and a heavy burden imposed on a patient. Also, since the small metallic electrode needs to be brought into contact with the target region of the myocardial tissue accurately to form the ablation line with the ablation catheter, a physician requires an advanced technique to manipulate the ablation catheter. Further, since the myocardial tissue is ablated in the dotted manner, an insufficient ablation line with spaces between the ablated regions may be formed, in which case the trigger region of the arrhythmia cannot be isolated completely, which may cause recurrence of the arrhythmia.
To solve the above problems, an ablation catheter with a balloon having a balloon at the tip portion of a catheter shaft has been developed recently, and an ablation catheter system with a balloon including a radio-frequency generator and a balloon surface temperature uniforming device has been reported (Patent Literature 2 and 3).
The ablation catheter system with a balloon is a system of inflating a balloon fixed to the tip side of a catheter shaft by a liquid for heating and heating the liquid for heating by a radio-frequency current supplied from a radio-frequency generator to ablate the entire myocardial tissue contacting the surface of the balloon (hereinafter referred to as balloon ablation).